Primal Desires
by Vampirerex1
Summary: Optimus gets desperate to void waste (pee), Rex lends a helping servo with explosive and pleasurable results. WARNING! This fic contains OMORASHI (Desperation and wetting), if you're not into that kind of thing, stop reading now. You HAVE been warned. Flamers will be doused in ice cold water. Thank you


**Author: **Vampirerex1  
**Category: **Movies - Transformers  
**Disclaimer: **I don't own Optimus or Rex, I'm just borrowing them for the sake of writing this fic.  
**Genre(s): **Romance/General  
**Note: WARNING! This fic contains Omorashi (desperation and wetting), if you're not into that kind of thing, then please stop reading. If you are, then please read on. You HAVE been warned, if you choose to ignore this warning and continue to read and are disgusted by what you read, that is at your own risk and I accept no liability for your scarred mind and eyes. Do not flame this story because 'it's disgusting', or 'it's gross', or whatever, you HAVE been warned.  
Pairing(s): **Optimus/OC  
**Rating: **R  
**Summary: **Optimus gets desperate to void waste, Rex lends a helping servo, with explosive and pleasurable results.  
**Title: **Primal Desires  
**Warning(s): CONTAINS OMORASHI**

**~Primal Desires~**

_**"You are kidding right?" She asked.**_

_**Optimus looked at her and then cycled his intakes.**_

_**"I do not believe it for a minute Rex but, the human soldiers have become wary. Tanya has…as the humans say…planted the seed of doubt in their minds" he replied.**_

_**Rex sighed and shook her head.**_

_**"And that seed has grown into a gigantic tree that is just filled with undeniable doubt" she stated.**_

_**Optimus nodded and Rex sighed again, before hanging her head.**_

_**"I hope Galloway knows what he's doing. I'm pretty much the only one here who's keeping Ironhide calm and in check. Not saying that you can't do it yourself, but…" she began.**_

_**Optimus once again cycled his intakes.**_

_**"I understand Rex, but I will do my very best to make sure this tree of doubt is demolished" he said.**_

_**Rex nodded again and turned to leave.**_

_**"Just remember that I love you all" she whispered.**_

_**The red and blue mech nodded and watched as she walked out of the door.**_

_**~Primal Desires~**_

It had been over a year since she had been practically kicked out of the Autobot base by Galloway and some of the other people on the base too. Of course, all of the Autobots hadn't believed a word Tanya had said to them about Rex being a Decepticon spy. Since then, Rex had made her-self a short living, she had found some work and had made some very good friends. Unfortunately, Rex hadn't been in contact with any of the Autobots, per Galloway's instructions, but recently, Rex had received word that she was allowed back on base, because a spy had been sent to watch over her and it had been confirmed that she wasn't a Decepticon spy.

So now she was walking into the Autobot base, after being picked up by Jolt, only to find Optimus, on his knees with Galloway shouting at him. She looked over at Will, who had just spoken to her, before she looked at Optimus, who also had his head resting against his left arm and his right hand clenched into a fist on his right thigh. As Will continued to speak, she held up her hand and waved him off while she began to walk towards Optimus.

"Optimus, what's wrong?" She asked.

The red and blue mech looked at her, his blue optics almost pleading with her. He'd been on his way to the waste extraction units to relieve himself, when Director Galloway had called him over for a meeting. Optimus always prided himself on his control of his body and functions, so he thought that he could simply hold off until the meeting with the director and general had finished. Sadly, things didn't turn out the way he wanted them too, and while the meeting went on, Optimus found himself getting more and more desperate to void, his desperation going from, well if one were to put it on a scale of one to ten, with one being not very desperate, five being desperate but manageable and ten being extremely desperate, he'd have to put his desperation at about eight and a half on that scale.

As time went by, Optimus found himself moving ever so slightly from pede to pede, it was so minute that it could simply be passed off as a change in position, but as time wore on, his movements became more noticeable and the desperation scale went up to a solid nine. Very soon he found himself in the position he was in now, on his knees, on the floor with one arm braced against the catwalk for support and one servo on his thigh. He knew that people would be alerted to his problem if he pressed his servo to his interface panel, so he tried to fight the urge, but by doing so, it was becoming harder and harder to hold himself, the scale now having increased to a nine and a half.

Rex looked up at Galloway, who was still shouting at Optimus, before dropping her bag and running towards the big mech. She climbed up his leg, jumped onto his arm, scrambled across his shoulders and jumped onto the bridge where Galloway was, before delivering a swift punch to his nose, making him shut up.

"You broke my nose!" He yelled.

She growled at him and walked towards him, grabbing him by his lapels and hoisting him up and looking into his eyes.

"Shut…up! Can you not see that there is something wrong with Optimus?" She asked.

Galloway looked down to Optimus and for once, actually saw the way Optimus was poised, before he narrowed his eyes.

"Why should I care about whether there is something wrong with that heap of Scrap Metal?" He asked back.

Rex's eyes turned blood red and she moved him so that he was dangling off the side of the platform, around a ten foot drop, that wouldn't kill him, but it would injure him quite badly. Galloway began to whimper as Rex began to growl at him, the kind of growl that an angry dog that was about to attack would do. Rex let her grip slacken a little and he moved a little, causing him to shout out and grab a hold of her wrist to at least try and save him-self.

"No, please don't" he begged.

Rex growled again and let her grip slacken once again.

"Give me one good reason as to why I shouldn't" she stated.

Galloway was about to say something, but instead Optimus' voice was heard.

"Rex…don't" he said.

The femme looked back at her boss at the sound of his strained vocals, before she pulled Galloway back onto the platform and growled again.

"Get out of my sight you pathetic little squishy" she hissed.

Galloway nodded and scrambled away, hurrying down the steps and out of the base in record time. Rex watched him go, before turning to Optimus. She watched as his right hand squeezed tighter with something that could be akin to pain, but what she didn't know was that a drop of processed energon had just escaped his spike and dribbled down his panel and to the floor. She walked around to where his arm was leaning against the platform and jumped down onto it, sitting on it, before looking at Optimus' face.

"What's the matter Optimus?" She asked.

She felt the muscle cables in his arm tense again as he clenched his fist, but she also saw the hand on his thigh open and move up slightly, as if he were going to place his hand in a very delicate place. After she saw said hand clench into a fist and a small, but clearly embarrassed moan escape her boss' vocals, her eyes went wide.

"Optimus, when was the last time you voided?" She asked.

The blue and red mech looked up at her and then put his head back onto his arm, being careful not to lean it against her legs, though he knew he wouldn't hurt her because of her being cybertronian, but still. He went to answer her, but a trickle of processed energon escaped him and he shuttered his optics. He was going to lose the battle with his tanks and void where he was sat if he wasn't careful. It wasn't that he was embarrassed about doing such a thing, its the fact that the humans on the base wouldn't take him seriously if he did lose all control of his body.

"I can't...hold it...any longer" he groaned.

Again Rex's eyes went wide and she jumped down, she needed to get him to the waste extraction units as soon as possible. The problem was, that they'd been built around the hidden side of the base, because there wasn't enough room on the base to put them. She turned towards her boss.

"I need you to follow me Optimus, can you do that?" She asked.

The Prime looked at her and nodded his helm once, following her first on his hands and knees to get out from under the catwalk and then slowly making his way to his pedes. However, as soon as he was at that vertical base, all pit let loose, the warnings in his processor alerted him to his impending disaster and he found himself running outside, just so he could clutch at his panel. He stood, with his back to the opening of the hangar and his servos wedged between his legs, he didn't notice Will coming out to see what was wrong.

"Optimus, are you alright?" He asked.

All the mech could do, was let out a groan of embarrassment, how in the name of Primus was he supposed to speak to Major Lennox when he had his servos in his intimate area? He couldn't, there was no way he'd be able to do that, William would never talk to him again, or at least he'd never be able to look at him in the same way again. He almost vented in relief when he heard Rex's voice.

"Major Lennox, you're wanted inside" she said.

Optimus couldn't see what happened, but he felt something touch his pede and looked down at Rex, a hint of purple creeping into his optics.

"I am sorry you have to see this Rex, not the welcome home party you were expecting I'm sure" he said.

Rex shook her head.

"Didn't want a party anyway, let's get you sorted before anything else" she said.

Optimus nodded and went to take a step forwards, but the cables that sealed off his waste tank decided to slacken a little and he groaned and bent over to at least try and stem the flow. Luckily, the cables tightened again and he was able to stand up straight, but as he went to take another step, he heard two engines and groaned. The twins, Mudflap and Skids would never let him live this down if they saw him in this predicament.

He looked down to Rex, who looked up at him and gave a sympathetic look.

"Sorry Optimus, you can't outrun them in your condition. I'll see if I can't hold them off while you make your way around to the waste extraction units" she said.

Optimus sent her a thankful nod and tried to slowly make his way to those wonderful units that extracted his waste. He turned his head to look back at Rex, but as he got close to the corner, he let out a yell as his cables began to give up the fight.

Rex, Mudflap and Skids looked around to where Optimus was and Rex had dread fill her spark.

"Oh no" she said.

She looked to the twins, before she transformed to her usual self and hurried over to Optimus, grabbing his servo in her own and running towards the waste extraction units, ignoring his protests. However, as soon as they got there, Optimus stopped still and Rex was pulled back by this. She looked to Optimus, who was just standing there with his optics offlined.

"Come on Optimus, almost there" she said.

The mech onlined his optics and looked at her.

"I can't...I can't move" he said.

He let out a whimper, something very unusual for Optimus and then there was the sound of liquid hitting the grass beneath him. Rex looked at him in shock, her boss, the great Optimus Prime nee Orion Pax, was, in essence, according to humans, wetting himself in front of her. As the flow from his panel slowed down and finally stopped, Rex walked up to him and, as the humans would do, she pulled him into a hug, one which he returned.

"I'm sorry Optimus" she said.

The mech cleared his vocals and then pulled away.

"It wasn't your fault Rex, you have nothing to apologise for" he replied.

Rex went to say something, but she heard two snickers and her optics turned red as she stalked around the corner, to see Mudflap and Skids there. She crossed her servos over her chest and raised an optic ridge.

"And what, if I may ask, is so funny?" She asked.

The younglings looked up and her and burst into laughter.

"Nothin' femme" Skids chuckled.

Rex then looked to Mudflap.

"Yeah, nothin' femme, 'cept yanno, Boss-bot peein' hisself" he said.

Rex growled and instantly the younglings stopped laughing.

"Really? Well that's not what I saw. All I saw, was Optimus doing what the humans call, taking a leak, outside next to the waste extraction units to appease me, I didn't see him soil himself. I believe you should go to Ratchet, have your optics checked, as you are quite clearly seeing things that are not happening. Now I suggest you move it before I pummel the both of you" she said.

The younglings just stood there.

"Now!" Rex growled.

They ran off and Rex went back around the corner to see Optimus leaning against the wall of the base with his panel open and waste dripping off his limp spike. The sight of it had her circuits heating up and her internal fans kicked in, producing a dull whirring sound. She shook her helm, getting aroused at this time wasn't appropriate for such a situation.

"Come on, I'll transform into my human form and give you a wash" she said.

Optimus looked at her and smiled slightly.

"Thank you Rex" he said.

The femme nodded and turned to walk into the hanger, when she heard a small groan. She stopped still and turned around to see Optimus moving his servo slowly over his spike which was already beginning to ooze lubricants. She swallowed and her internal fans clicked up another speed, the whirring louder.

"Optimus?" She asked.

The mech just looked at her, his optics going from brilliant cerulean to violet in lust. Rex was frozen, she was a femme that had many kinks and many things that...turned her on...for lack of a better phrase, seeing Optimus void involuntarily had aroused her to a manageable level, but now seeing him stroking his large spike, it was enough to send a rush of lubricants to her port and to get her circuits buzzing with needed overload. Not only that, but her spark was pulsing madly behind its casing, wanting to merge with Optimus' spark. The large mech stood up straight and walked over to her, his servo still pumping his spike.

"I can smell you Rex, you became aroused by watching me involuntarily void didn't you?" He asked.

His vocals had dropped an octave, sending shivers up her spinal strut and causing her fans to click onto the third and final level. With her fans now working at full power and lubricants rushing to her port, she couldn't do much else except curse the mech in cybertronian before grabbing his shoulders and slamming him into the wall of the base, not caring what attention it brought from the humans.

"You're a brave mech Optimus" she muttered.

She slammed her lip plates to his, the sound of scraping metal heard as she also ran her servos over his chest plates, earning a wanton moan from the mech beneath her. Suddenly the large mech pushed her off and sheathed his spike before transforming and driving off towards a clearing that was well away from any human activity. Rex transformed and followed him, her engines roaring as she sped behind him and her fans still working at full power.

Upon arriving at the clearing, Optimus transformed and turned towards where Rex was going to enter, only to be barrelled over by a very needy femme. The two rolled around the grass for a few minutes before Optimus got the upper hand and pinned her to the ground, his panel sliding back and exposing his spike to her. The large organ rested against her abdominal plates, where he lightly began to thrust his hips as his servo extensions traced around the seams of her own panel, which in turn slid back to reveal her port.

"How shall we do this my love, with or without the armour?" He asked.

His voice was calm, but his optics betrayed how needy he was, in the year she'd been missing, he and the other mechs she'd mated with had been having a hard time finding any kind of release, especially with Tanya around. That femme treated all the mechs like they were her pets, telling them what they could do and what they couldn't do. He knew that Ironhide, Ratchet, Mirage and Jazz were in a similar predicament as he was and most probably in a similar predicament as he had been. Tanya didn't seem to like letting them void waste without her knowing where they were going, what they were doing and how long they would be.

Shaking his helm to rid himself of thoughts about Tanya, Optimus looked down at the femme beneath him and growled at the way she was squirming wantonly. As if to tease her, he pushed one of his servo extensions into her port while simultaneously pushing one into her valve, making her shriek in pleasure and pain. He smiled before removing both of his servo extensions and instead placing the tip of his spike at her port.

"What do you want Rex?" He asked.

Rex growled up at him, her optics a very light crimson in unabashed lust. As he waited for her to speak, he rotated his hips, making his spike trace the rim of her port, teasing her more as well as teasing himself.

"For the love of Primus, just frag me Optimus!" She hissed.

As if that were his godsend, the Prime thrust himself into her, groaning at the tightness of her port. He couldn't remember if she'd always been this tight or if a year without any interfaceary activity made her just that little bit tighter. He paused for a few seconds, before he started up a brutal and fast pace, his helm going down to her shoulder and his lip plating dragging a wire into his mouth where he bit down on it with his dentas. Hearing her growl spurned him on and his thrusts quickly became erratic, so long without overload, he could feel that they were both ready to burst within minutes of him entering her. Leaning up, the blue and red mech opened his chest plates, with a simple nonverbal command and he watched as she did the same. As they both neared the edge, their sparks began to dance together, as if doing the ballroom blitz before they merged together as both overloaded simultaneously.

Optimus held himself over Rex as his spike emptied his fluids into her and his spark retreated into his chest causing his chest plates to immediately close behind it. Slowly, his spike began to depressurize and his optics returned to their usual cerulean colour and her optics returned to their usual violet colour as her own spark retreated into its casing and her chest plates closed over it.

"Wow" Rex said.

Optimus chuckled and rolled off of her, his panel clicking back into place at the same time as hers did. He pulled her to him and pressed a kiss to her lip plates, blinking his optics a little before giving a deep air intake which was the cybertronian version of a yawn.

"Wow indeed Rex, wow indeed" he said.

They both then fell into a light recharge state, knowing that Rex would be interfacing four more times if Tanya had done to Ironhide, Ratchet, Mirage and Jazz what she'd done to Optimus.

_**~Primal Desires~**_

_**A/N: Okay so I've been wanting to write this for a while, I've seen a few watersports/Omorashi stories out there and didn't find any for Transformers, (Except one which was between Megatron and Starscream which was a good read, but didn't quite hit the spot), so I decided to write my own. Now I'm aware that many people find the act of Omorashi, or wetting one's undergarments and clothing absolutely disgusting, but let me tell you that it is a real "fetish" and those who do enjoy it, do so privately because it's not seen as the social norm. Personally I don't see a problem with it, arousal is arousal at the end of the day and whatever floats your boat...if it works and you're happy with it, then why not? Anyway, this will be a one shot, unless I get reviews asking to see the desperation of Ratchet, Ironhide, Jazz and Mirage, but if I don't then this'll be the only one I write. **_

_**Now...I HAVE warned you at the top of this story, so don't come whinging and whining to me that this story is aboslutely disgusting and shouldn't have been written and now that you've read it your mind is scarred for life. Not my problem, if you chose to ignore the warnings at the start of this story, on your head be it, don't dampen the reading for other people with your poxy flames. As with any fire, flames can be doused with water or sand, cut off their oxygen, they die. So flamers will be ignored and doused with ice cold water.**_

_**Thank you for reading and enjoy**_

_**Vampyrex1**_


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